Not being the technical type today I did a quick comparison of these four rounds. Not knowing what the "proper" procedure is this is what I did -- started with a clean bore, fired 2 fouling rounds, shot one 20-round string, let rifle cool for 10 minutes, cleaned bore, and started the process over again. The rifle was a Bushmaster chrome lined 5.56 with a 14.5" barrel and a KKF A3 TakBrake attached. Chrono screens (2 ft spacing) were 10 ft from muzzle. Weather conditions: Clear sunny sky, winds calm, temp was 54 degrees F, at an elevation of 4950 ft. While only a total of 84 rounds were fired there were no failures to fire or failures to extract.

If I had it to do over again and more time available I would have liked to have fired two different lots of each brand with two 20-round strings of each through a 14.5" barrel and a 20" barrel. Also I realize there is more to a round than velocity. For one accuracy was not measured. After doing this I have a better idea what a more "complete" test would cover. Hopefully this information is somewhat useful.

Originally Posted By Siglite:
Thanks for the research. The info you have posted has helped me make up my mind on my next ammo order.

View Quote

FWIW, velocity alone should NOT be the only criteria used when selecting your SHTF ammo.
The most reliable that shoots the tightest groups is what I base my SHTF ammo choice on.
There is no possible way to know which shoots the tightest or is most reliable in your rifle until you test it.
Mike

EXCELLENT DATA READYMAN! Thank you! Although, the cleaning wasn't really necessary.. the difference any fouling would make would be so incredibly minimal. I find it really odd that you got such low velocity numbers for Q3131A. Maybe just an underloaded lot or something? Anyway, thank you again!

Originally Posted By Siglite:
Thanks for the research. The info you have posted has helped me make up my mind on my next ammo order.

View Quote

FWIW, velocity alone should NOT be the only criteria used when selecting your SHTF ammo.
The most reliable that shoots the tightest groups is what I base my SHTF ammo choice on.
There is no possible way to know which shoots the tightest or is most reliable in your rifle until you test it.
Mike

View Quote

Thanks Mr. Wilson. I'm planning on taking your advice. I have shot some Q3131a, and it groups really well in my rifle. I have been told that Q3131a is manufactured by IMI. I was thinking that the IMI M193 with it's lower SD would be slightly more accurate and that is why I am really exited about this test that Readyman posted. I like velocity, but I also like consistency. I am looking to get a case of the IMI M193,and if it shoots as good or better than the Q3131a I will order more.
Thanks for the info and help!

Originally Posted By underdog75:
Thanks...I also find the Q3131a numbers a little low....XM193 usally runs right at 3000 for me(RRA 16") with the Q3131a a few ticks behind,usally around 2970fps....UNDERDOG

View Quote

Wow, that's incredibly low for a 16". Are you at sea level in the freezing cold or something? You measuring 50 yards from the muzzle? Most 16"'s get ~ 3100fps with XM193 and about 30-50fps lower with Q3131A. Readyman has a 14.5" barrel and is matching your numbers.
Also, we're not talking about 30-50fps in Readyman's test. His lot of Q3131A ran over 110fps slower than XM193. It even ran slower than the South African stuff. I've never seen that happen. I'm wondering if it's a typo or if he got a REALLY downloaded lot.

Isn't standard deviation a good indicator or repeatability and therefore accuracy? I know there are too many variables to say for sure, but overall wouldn't the M193 be more accurate (tighter groups) in more rifles than the others?

Originally Posted By underdog75:
Thanks...I also find the Q3131a numbers a little low....XM193 usally runs right at 3000 for me(RRA 16") with the Q3131a a few ticks behind,usally around 2970fps....UNDERDOG

View Quote

Wow, that's incredibly low for a 16". Are you at sea level in the freezing cold or something? You measuring 50 yards from the muzzle? Most 16"'s get ~ 3100fps with XM193 and about 30-50fps lower with Q3131A. Readyman has a 14.5" barrel and is matching your numbers.

View Quote

Number takin at around 200-300" ASL @ 60degF...
Its the only 16" barrel i have so i cant compare...Or it COULD be the 7000 rounds down the bore?[;)]........UNDERDOG

[quote]Originally Posted By Knife_Sniper:
If it doesen't die after 20 rounds of 7.62x51, it don't die.[/quote]

Originally Posted By ptaylor:
Isn't standard deviation a good indicator or repeatability and therefore accuracy? I know there are too many variables to say for sure, but overall wouldn't the M193 be more accurate (tighter groups) in more rifles than the others?

I double checked to make sure there were not any typos (in particular the Q3131A results) and it turns out all entries in the original post are correct. In the Q3131A 20-round string there were only 4 rounds that exceeded 2900 fps (2916, 2908, 2904, and 2902). Next I plan on testing two different lots each of Q3131A, XM193, and M193 with rifles having 14.5", 16", and 20" barrels. Several pointed out the cleaning process was not necessary so that will help speed things up. If there is anything else I need to do to improve the usefulness of this test please pass it on. The weather here in central Wyoming has turned quite cold so it will probably be a week or two before the weather breaks and it warms up a bit. I'll post the results when completed and thanks in advance for any suggestions you might have.

FWIW, Remington's ballistics section has a note about the effect of barrel length on velocity, and estimates that in the 3000-3500 fps range, each inch of barrel length is worth about 30 fps.
So extrapolating from a 14.5" to a 20" barrel should mean another 160 to 170 fps.